Process of endosteal fixation of a ligament

ABSTRACT

A cannulated interference screw (10) and process for human implantation in an arthroscopic surgical procedure for replacement of a ligament, or the like. The interference screw is provided with a drill end (11) that extends longitudinally from an end of a cylindrical body (14), which drill end includes equally spaced flutes (12) therearound. The flutes extend into first and second cutting threads (15a) and (15b), respectively which cutting threads and threads (15) are formed around the cylindrical body. A center longitudinal passage (16) is formed through the interference screw drill end and cylindrical body, which passage is stepped outwardly within the cylindrical body into a hexagonal sided section (18) that is for receiving a sided end (20) of a driver (19) that is fitted therein. In practice, the cannulated interference screw is installed by sliding it along a guide rod (25) that is fitted in a prepared ligament tunnel (22) through a bone mass, alongside a bone block portion of a ligament (23) within the bone endosteum, which ligament is maintained in that tunnel under tension. The driver is also holed longitudinally to travel along the guide rod to fit into and turn the interference screw, providing fixation of the ligament in that tunnel.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to fixation devices and more particularly toarrangement for anchoring a ligament in a bone mass.

2. Prior Art

Until recently, in ligament repair and/or replacement surgery involvingsecuring of one or both ligament ends to a bone mass have beenaccomplished utilizing staples, or like fixation devices, that aredriven through or across the ligament and into the bone mass. Suchligament anchoring has involved connecting the ligament end to the bonemass exterior, requiring, for a knee cruciate ligament procedure, thatthe replacement ligament end or ends extend onto the periosteum oroutside bone surface beyond a ligament tunnel with each end bent andsecured onto the bone mass surface. Such ligament bending, of course,may result in a force concentration at that bend, weakening andpotentially subjecting the ligament to rupture.

An earlier patent issued to two of the present inventors in a "SutureAnchor Assembly", U.S. Pat. No. 4,632,100, addresses anchoring a sutureto a bone mass surface for joining a ligament thereto, but does notaddress securing a ligament in a ligament tunnel, as does the presentinvention. Another patent issued to two of the present inventors in a"Ligament Attachment Method and Apparatus", U.S. Pat. No. 4,772,286 doesinvolve an endosteal fixation device for securing, at a certain tension,a ligament in a ligament tunnel. End coupling arrangements including athreaded flattened cone, expanding cone, and threaded cylindrical endanchors, that are taught by this patent, however, are structurally andfunctionally unlike the present invention. Also, still another inventionof two of the present inventors in a "Ligament Anchor System", filed asa U.S. patent application, Ser. No. 289,728 is also an endostealfixation system that includes a sleeve for turning in a tapped cortex,the sleeve to receive a footing turned therein that mounts a ligament.None of the inventions set out in these patents or in the patents citedtherein or as were cited during the individual applicationsprosecutions, however, involve wedging a ligament bone block portion ina ligament tunnel as taught by the present invention.

The interference screw of the present invention is similar inconstruction to the anchor shown and described in the above-cited U.S.Pat. No. 4,632,100 of two of the present applicants, in that bothinvolve a threaded cylindrical body with a forward fluted drill end. Thepatented anchor, of course, is for turning into a bone mass, whereas theinterference screw of the present invention is cannulated for guidedtravel on a guide wire by a driver into ligament tunnel, alongside aligament fitted therein. The interference screw of the present inventionis principally for wedging between a bone block portion of a ligamentand tunnel wall, and is accordingly both structurally and functionallyunlike the patented anchor.

BRIEF SUMMARY OF THE INVENTION

It is therefore a principal object of the present invention in aninterference screw and system to provide a device for endosteal fixationor the surface of a bone block portion of a ligament and the wall of aligament tunnel formed through a bone mass.

Another object of the present invention is to provide a cannulatedinterference screw having a drill end for both drilling a hole into abone mass followed by the interference screw threads, which threads haveat least one leading thread for cutting into that drilled hole.

Another object of the present invention is to provide an arrangement forguiding the cannulated interference screw between a ligament tunnel walland the bone block portion of a ligament installed therein.

Still another object of the present invention is to provide a driver andguide wires for precisely and conveniently turning the interferencescrew between a ligament tunnel wall and the bone block surface of aligament fitted therein, the driver and guide wire also providing anarrangement for conveniently removing the interference screw.

Still another object of the present invention is to provide a simple andreliable device and system for fixing a bone block portion of a ligamentwithin a ligament tunnel that is formed through a bone mass.

In accordance with the above objects, the present invention is in aninterference screw and a system for its use to provide for securing abone block portion of one or both ligament ends under tension within aprepared ligament tunnel that has been passed through a bone mass. Inpractice, a ligament tunnel, as for example, an anterior or posteriorcruciate ligament tunnel is prepared in the distal femur and proximaltibia portions of a patient's knee in an arthroscopic surgicalprocedure. In that procedure a surgeon monitors drilling progress on afluoroscopic monitor, or the like. The procedure involves both preparingthe tunnel through both the distal femur and proximal tibia bone endsand installing either an allograft or prosthetic ligament, in thatprepared tunnel. Wherein, that ligament is maintained under tension.

The interference screw of the present invention is to secure a boneblock portion of the ligament end or ends in the tunnel. Theinterference screw preferably includes a cylindrical body with a fluteddrill on a forward end and is threaded from that fluted drill to a rearend. The flutes of the drill are cut into the adjacent threads toprovide self-tapping sharp cutting edges, that follow the fluted drillinto a bone mass. Also, the interference screw is cannulated, having acenter longitudinal passage therethrough that is sided on a rear endopposite to the fluted drill end to receive a driver fitted therein.

The cannulated interference screw and driver are to slide and turn alonga guide wire that is fitted into the ligament tunnel, alongside the boneblock portion of the ligament positioned therein. The driver turns theinterference screw along the ligament tunnel wall and ligament surface,as viewed on the fluoroscopic monitor, to where the interference screwis appropriately positioned so as to provide an interference fittherebetween. Whereat, the drive and guide pin are removed.

The cannulated interference screw is removed by reinserting the guidepin with the driver telescoped thereon along the ligament tunnel andinto the interference screw longitudinal cavity, the drive to fit intothe interference screw for turning it out of the ligament tunnel.

DESCRIPTION OF THE DRAWINGS

In the drawings that illustrate that which is presently regarded as thebest mode for carrying out the invention:

FIG. 1 is a profile perspective view of the present invention in acannulated interference screw;

FIG. 2 is a side elevation view of the cannulated interference screw ofFIG. 1 showing, in broken lines, that a longitudinal passagetherethrough is stepped outwardly into a sided rear end cavity;

FIG. 3 is a rear end elevation view of the cannulated interference screwof FIG. 1;

FIG. 4 is a forward end elevation view of the cannulated interferencescrew of FIG. 1;

FIG. 5 is a profile perspective view of a patient's knee with a portionof the distal femur shown broken away that includes a ligament tunnelformed through the knee and showing an anterior cruciate ligamentmaintained in tension therein, the cannulated interference screw of FIG.1, shown fitted to slide along a guide rod that is passed from the femurcortex ligament tunnel end, traveling alongside a bond block portion ofthe ligament; and

FIG. 6 is a view of a section of the bone block portion of the ligamentand cannulated interference screw with guide rod of FIG. 5, and showinga driver that is telescoped over the guide rod that has a sided end forfitting into the sided end of the cannulated interference screw end.

DETAILED DESCRIPTION

FIG. 1 shows a preferred embodiment of a cannulated interference screw10 of the present invention, hereinafter referred to as screw. The screw10, as shown best in FIGS. 1 through 4, includes a drill 11 that extendslongitudinally from its forward end that preferably incorporates three(3) longitudinal flutes 12 arranged at one hundred twenty (120) degreeintervals around the drill. The flutes 12 extend from a drill forward ornose end 13 that, as shown at A in FIG. 2, is angled rearwardly atapproximately a thirty (30) degree angle to the vertical. Each flutetapers outwardly along the drill 11, as shown at B in FIG. 2, atapproximately a ten (10) degree angle from the horizontal. The flutewalls are shown to taper together passing into forward cutting threads15a and 15b of threads 15.

Threads 15 are formed around a cylindrical screw body 14. Shown best inFIGS. 1, 2, and 4, the flutes 12 are shown to be spaced at one hundredtwenty (120) degree intervals from drill nose end 13 to pass throughfirst and second cutting threads 15a and 15b, respectively. The cuttingthread 15a is shown to have a lesser outside diameter than that ofcutting thread 15b, and the other threads 15. The intersection walls ofthe cutting threads 15a and 15b at flutes 12 from walls that arepreferably angled at approximately right angles to the vertical axis ofthe thread as cutting edges. Thereby, in turning the screw 10 into abone mass, the drill 11 will form a hole and travel into that bone massto where the first cutting thread 15a, at its intersection to one of thedrill flutes 12 will contact and cut into that bone mass. The secondcutting thread 15b follows the first to further deepen the cut thread toreceive the following individual threads of threads 15 turned therein.Accordingly, the arrangement of drill 11 and threads 15 provide a singledevice for drilling, tapping and seating in a bone mass. Also, while, asshown best in FIG. 2, the threads are preferably tapered, they need notbe within the scope of this disclosure.

Shown in broken lines in FIG. 2, the drill 11 and screw body 14 includea center longitudinal passage 16 therethrough that is preferably steppedoutwardly at 17 into a sided rear section 18. The sided rear section 18walls are preferably hexagonal to receive, as shown in FIG. 6, ahexagonal shaped end 20 of a driver 19 that is fitted therein forturning screw 10. Which driver opposite end 21 is arranged to receive achuck of a tool, not shown, that is either manually or motor driven forturning the driver, as set out below.

FIG. 5 shows a patient's knee with a portion of the distal femur cutaway, exposing an anterior cruciate ligament tunnel 22, hereinafterreferred to as ligament tunnel, that is formed therein, and extendsacross the knee through both the distal femur and proximal tibia. Theligament tunnel is shown to open at the tibial tuberosity andanterolateral femoral cortex ends of that ligament tunnel. The ligamenttunnel 22 is preferably formed by conventional surgical procedures, suchas, for example, the procedure set out in the patent of two of theapplicants, U.S. Pat. No. 4,772,286, or by like procedure, within thescope of this disclosure.

As shown in FIG. 5, a ligament 23, that can be a prosthetic or allograftligament, or the like, is fitted into the ligament tunnel 22. Sutures 24are shown connected to the ligament ends that extend out from theligament tunnel ends and are for use in applying a tensile force on theligament. So arranged, to install the screw 10 for providing aninterference fit between the ligament tunnel 22 wall and a bone blockside portion of ligament 23, a surgeon, observing on a fluoroscopicmonitor, or the like, fits a guide rod 25 through an end of the ligamenttunnel 22, sliding it along the bone block portion of the ligament.

With the guide rod 25 installed as shown in FIG. 5, a surgeon can fit ortelescope the longitudinal passage 16 of screw 10 onto the guide rod 25.A center passage 26 of the driver 19 is then fitted or telescoped ontothat guide rod, and passed therealong until the driver sided end 20 fitsinto the sided end 18 of the screw longitudinal passage 16. The driver19 is then mounted to the drill 11 end 13 for turning into and betweenthe ligament tunnel 22 and ligament 23 providing an endosteum orendosteal fixation therebetween. In that turning, the screw 10 travelsto the attitude shown in FIGS. 5 and 6. Whereat, the guide rod 25 can bepulled out of the screw and ligament tunnel providing an endosteum orendosteal fixation, the screw installed therein prohibiting the boneblock portion of the ligament 23 from being pulled out of that ligamenttunnel 22. In practice, the screw 10, installed as shown in FIG. 5, hasprohibited a bone block portion of the ligament 23 from removal fromligament tunnel 22 to an applied tensile force of approximately onehundred fifty (150) pounds. Which force is well above a maximumanticipated tensile stress in running of approximately eighty (80)pounds.

It should be understood that the installation of the screw 10 in theproximal tibia portion of the ligament tunnel 22 is like that describedabove for screw installation in the distal femur portion of thatligament tunnel. Also, as desired, within the scope of this disclosure,more than one screw per tibial and femoral endosteum ligament tunnelsections can be used for increasing ligament holding strength, asdesired and, rather than fitting the screw into the ligament tunnel,alongside the bone block portion of the ligament, a hole can be drilledacross the ligament tunnel, through the bone block portion and the screwturned therethrough.

The screw 10 is preferably manufactured from a material that is suitablefor sterilization and human implantation and, in practice, the preferredscrew is manufactured from a titanium or type 316 stainless steel. Itshould, however, be understood, screw 10 can be manufactured from anymaterial that is suitable for human implantation, to include abio-degradable material such as a bio-erodible plastic, or the like,providing such a biodegradable material is sufficiently hard to providethe described functions.

While a preferred embodiment of the invention in an interference screwand its use has been shown and described herein, it should be apparentthat this disclosure is made by way of example only and that variationsto the invention are possible within the scope of this disclosurewithout departing from the subject matter coming within the scope of thefollowing claims and a reasonable equivalency thereof, which claims weregard as our invention.

We claim: .[.
 1. A process of endosteal fixation of a ligament withinthe interior of a bone mass comprising, forming a ligament tunnelthrough adjacent bone masses; fitting a ligament under tension in saidligament tunnel, extending between said adjacent bone masses; andturning a threaded device into one end of said ligament tunnel, guidingit alongside the ligament, such that the threads of said threaded deviceturn into said tunnel wall and a bone block end portion of saidligament..].
 2. A process of endosteal fixation .[.as recited in claim1.]. .Iadd.of a ligament within the interior of a bone mass comprising,forming a ligament tunnel through adjacent bone masses; fitting aligament under tension in said ligament tunnel, extending between saidadjacent bone masses; and turning a threaded device into one end of saidligament tunnel, guiding it alongside the ligament, such that thethreads of said threaded device turn into a wall of said tunnel and abone block end portion of said ligament.Iaddend., wherein the threadeddevice is cannulated and is .[.arranged for travel and turning.]..Iadd.guided .Iaddend.along a guide wire that is fitted into theligament tunnel, alongside the ligament. .[.3. A process of endostealfixation as recited in claim 1, wherein the threaded device has athreaded body and includes a drill extending from one or a first endwith an arrangement for fitting a driver formed in the other or secondend..].
 4. A process of endosteal fixation .[.as recited in claim 3.]..Iadd.of a ligament within the interior of a bone mass comprising,forming a ligament tunnel through adjacent bone masses; fitting aligament under tension in said ligament tunnel, extending between saidadjacent bone masses; and turning a threaded device into one end of saidligament tunnel, guiding it alongside the ligament, such that thethreads of said threaded device turn into a wall of said tunnel and abone block end portion of said ligament.Iaddend., wherein .Iadd.thethreaded device has a threaded body and includes a drill extending fromone or a first end with an arrangement for fitting a driver formed inthe other or second end and .Iaddend.the threaded device and driver areboth cannulated .[.to travel.]. .Iadd.and guided .Iaddend.along a guidewire that is .[.for fitting.]. .Iadd.fitted .Iaddend.into the ligamenttunnel, alongside the bone block end portion of the ligament. .Iadd.5. Aprocess of endosteal fixation of a ligament within the interior of aknee comprising:forming a tunnel, having an interior wall, through atibia and an adjacent femur; fitting a ligament secured between two boneblocks into said tunnel; fitting a guide wire into said tunnel alongsideone of said bone blocks; telescoping a cannulated interference screwover said guide wire; telescoping a cannulated driver over said guidewire to engage a rear end of said interference screw with said driver;and turning said driver so as to turn said interference screw causingcutting threads on said interference screw to dig into the tunnel walland said one of said bone blocks. .Iaddend. .Iadd.6. A method accordingto claim 2, wherein the threaded device has a generally cylindrical bodyand threads formed about the body from a last thread extending from therear of the body to a first thread, the first thread having a smallerouter diameter than the last thread, and wherein the threads form theradially outermost projection from the body. .Iaddend. .Iadd.7. A methodaccording to claim 5, wherein the interference screw has a generallycylindrical body and threads formed about the body from a last threadextending from the rear of the body to a first thread, the first threadhaving a smaller outer diameter than the last thread, and wherein thethreads form the radially outermost projection from the body. .Iaddend.